Antonyms of adj foolish

2 senses of foolish

Sense 1
foolish (vs. wise) -- (devoid of good sense or judgment; "foolish remarks"; "a foolish decision")

wise (vs. foolish) -- (having or prompted by wisdom or discernment; "a wise leader"; "a wise and perceptive comment")
        => all-knowing, omniscient -- (infinitely wise)
        => perspicacious, sagacious, sapient -- (acutely insightful and wise; "much too perspicacious to be taken in by such a spurious argument"; "observant and thoughtful, he was given to asking sagacious questions"; "a source of valuable insights and sapient advice to educators")
        => owlish -- (resembling an owl; solemn and wise in appearance)
        => sapiential -- (characterized by wisdom, especially the wisdom of God; "a sapiential government")
        => sage -- (having wisdom that comes with age and experience)

Sense 2
anserine, dopy, dopey, foolish, goosey, goosy, gooselike, jerky -- (having or revealing stupidity; "ridiculous anserine behavior"; "a dopey answer"; "a dopey kid"; "some fool idea about rewriting authors' books")

INDIRECT (VIA stupid) -> smart -- (showing mental alertness and calculation and resourcefulness)

Similarity of adj foolish

2 senses of foolish

Sense 1
foolish (vs. wise) -- (devoid of good sense or judgment; "foolish remarks"; "a foolish decision")
       => absurd, cockeyed, derisory, idiotic, laughable, ludicrous, nonsensical, preposterous, ridiculous -- (incongruous;inviting ridicule; "the absurd excuse that the dog ate his homework"; "that's a cockeyed idea"; "ask a nonsensical question and get a nonsensical answer"; "a contribution so small as to be laughable"; "it is ludicrous to call a cottage a mansion"; "a preposterous attempt to turn back the pages of history"; "her conceited assumption of universal interest in her rather dull children was ridiculous")
       => asinine, fatuous, inane, mindless, vacuous -- (devoid of intelligence)
       => cockamamie, cockamamy, goofy, sappy, silly, wacky, whacky, zany -- (ludicrous, foolish; "gave me a cockamamie reason for not going"; "wore a goofy hat"; "a silly idea"; "some wacky plan for selling more books")
       => fond -- (absurd or silly because unlikely; "fond hopes of becoming President"; "fond fancies")
       => harebrained, insane, mad -- (very foolish; "harebrained ideas"; "took insane risks behind the wheel"; "a completely mad scheme to build a bridge between two mountains")
       => ill-conceived, misguided -- (poorly conceived or thought out; "an ill-conceived plan to take over the company")
       => rattlebrained, rattlepated, scatterbrained, scatty -- (lacking sense or discretion; "his rattlebrained crackpot ideas"; "how rattlepated I am! I've forgotten what I came for"- Glenway Westcott)
       => unwise -- (showing or resulting from lack of judgment or wisdom; "an unwise investor is soon impoverished")
          Also See-> impolitic#1; imprudent#1; inadvisable#1, unadvisable#1; ill-advised#1, unadvised#1

Sense 2
anserine, dopy, dopey, foolish, goosey, goosy, gooselike, jerky -- (having or revealing stupidity; "ridiculous anserine behavior"; "a dopey answer"; "a dopey kid"; "some fool idea about rewriting authors' books")
       => stupid (vs. smart) -- (lacking or marked by lack of intellectual acuity)